Food, dietary components, and fluid volumes with which a drug is ingested have been shown to influence the rate and extent of drug absorption after oral administration. Food generally retards or inhibits gastrointestinal drug absorption. Fat appears to delay absorption due to delayed gastric emptying but some proteins and carbohydrates may reduce absorption by binding or complexation phenomena. Some drugs appear to be absorbed more efficiently from dilute solutions than from concentrated solutions. However information on the influence of solution volume on drug absorption is scarce and conflicting. In this proposal the influence of various solid diets and also solution volumes on drug availability will be studied under carefully controlled conditions in man. Acidic, basic or essentially neutral drugs, which are currently extensively used, will be investigated. The research is in two sections. In the first, drug will be administered as tablets or capsules before, with or after normal, high protein, high fat or high carbohydrate test meals. In the second section drugs will be administered together with various water volumes. Drug availability will be estimated by assaying for drug in blood or plasma at suitable times after dosing. Absorption rates and relative bioavailability will be calculated by computer using standard pharmacokinetic techniques, or modifications of these. Data will be analyzed statistically. The major objectives of the research are to obtain a clearer understanding of the influence of the above factors on drug absorption characteristics and to provide information leading to improved, more reproducible drug therapy in man and greater control of drug efficacy studies in man.